The invention relates to a method and an apparatus for making a trim component and especially an interior trim panel for a motor vehicle, wherein the decorative covering of the trim component includes two different cover materials.
In the automotive industry, it has become known to use interior trim components such as interior door panels, dashboards, and the like having a decorative covering including two different cover materials on the same trim component. Such a trim component having a two-part cover material is desired by consumers, for example to achieve a xe2x80x9ctwo-tone effectxe2x80x9d in which the two different cover materials have different colors, or a high value or xe2x80x9cluxury effectxe2x80x9d in which the two different cover materials are different types of materials such as a decorative cover film and a decorative cloth, or in which the different cover materials have different degrees of xe2x80x9csoft touchxe2x80x9d padding or the like.
In order to make such vehicle trim components having two-part cover materials, it has conventionally been the practice to splice together the two different cover materials before applying the spliced cover sheet onto the substrate of the trim component. The splicing of the two different cover materials has conventionally been carried out by thermal welding, adhesive bonding, or stitching. After the two different cover materials have been spliced together in such a manner, it is generally necessary to hide or cover the splice line in order to hide the stitching or any adhesive overspill or the like. This is conventionally achieved by applying a trim strip, such as a strip of plastic, chrome, wood or the like, over the splice line on the finished trim component. Alternatively, it has been attempted to press the splice line into a groove provided in the substrate in order to hide the splice line in this manner.
The above described conventional practices and the resulting trim component having a two-part cover material suffer many disadvantages, including the following. The preliminary process of splicing together the two different cover materials involves extra processing and handling steps, which translates into increased costs and a greater likelihood of defective parts leading to a higher reject rate. Furthermore, the application of a trim strip to hide the splice line on the finished door panel, dashboard or the like requires extra steps and extra materials, which again lead to higher costs and higher defect rates.
Most importantly, the previously known methods for making a trim component having a two-part cover material require extreme precision in forming the splice between the two different cover materials, then aligning the spliced two-part cover material onto the substrate of the trim component, and aligning the splice line with the groove provided in the substrate and/or aligning the splice trim strip with the splice line. It has been found in practice that this high degree of precision cannot be reliably attained, and as a result, the splice line is left at least partially visible in the finished trim component, i.e. the splice line protrudes out of the groove in the substrate or protrudes from under the splice trim strip. This leads to an unacceptably high reject rate of the finished trim components.
Moreover, in the operation for pressing the splice line into a groove provided in the substrate, it has been necessary to preform the groove in the substrate, which requires extra processing steps, and it has been necessary to make the groove wide enough to provide a sufficient tolerance range so that a tucking blade can press the splice line of the cover material down into the groove and then be retracted. In other words, the groove in the substrate conventionally has to be wide enough to allow for the thickness of the two layers of the cover material on both sides of the splice and for the thickness of the tucking blade that presses the cover material into the groove. After the tucking blade is retracted, however, a gap necessarily remains where the tucking blade had been pressed in. In any event, the result in the finished trim component has been unsatisfactory, because of the above mentioned defects in alignment of the splice line with the groove, but also because of the width of the conventional groove, which does not have a xe2x80x9cclosedxe2x80x9d and xe2x80x9ccrispxe2x80x9d appearance.
In view of the above, it is an object of the invention to provide a trim component especially for the interior of a motor vehicle, that has a decorative covering including at least two different cover materials in which the two cover materials are not pre-spliced together, and the junction line is hidden in a groove or valley of the substrate without requiring a splice trim strip. It is a further object of the invention to provide a method and an apparatus for producing such a trim component, which avoid the need for pre-splicing operations, and which ensure that the junction line between the two cover materials is precisely positioned and received in the groove of the substrate. The invention further aims to avoid or overcome the other disadvantages of the prior art, and to achieve additional advantages, as apparent from the present description.
The above objects have been achieved in a trim component according to the invention, including a substrate, and a decorative covering including two different cover sheets, which may include cover sheets having different colors and/or cover sheets made of different materials, such as a cloth cover sheet and a film cover sheet. The film may be a synthetic leatherette film, or a vinyl film, or a thermoplastic polyolefin (TPO) film, for example. The cover sheet may include a polyolefin foam or film backing for achieving hot-melt bonding. The substrate preferably comprises natural fibers and a polyolefin material, and especially polypropylene. An example of a preferred material is a multi-layered substrate material available under the trademark xe2x80x9cLOPREFINxe2x80x9d from R+S Technik GmbH of Offenbach, Germany.
The substrate includes a valley formed therein, with a junction of the two different cover sheets pressed into this valley. The two different cover sheets are not pre-spliced to each other, but instead are simply pressed into the valley as it is being formed. Particularly, the valley is formed by pinching the substrate material onto the junction area of the two different cover sheets as the substrate is being molded and laminated with the cover sheets.
The cover sheets are laminated and adhered onto the substrate due to the hot-melt adhesion effect provided by the surface of the hot substrate during the forming process. Namely, when the substrate material is heated for laminating, the polypropylene therein is softened and at least partially melted to provide a tacky adhesion for bonding the two cover sheets onto the substrate, and also into the valley of the substrate. Thus, no additional stitching or adhesive is necessary for joining the two cover sheets to each other or for bonding the cover sheets onto the substrate.
The above objects have generally further been achieved by a method according to the invention of the above-referenced parent application Ser. No. 09/176,356, now U.S. Pat. No. 6,124,157, of the present Continuation-In-Part. According to the general method which is common to the parent application and the present Continuation-In-Part, the two different cover sheets are separately laid onto a preheated substrate sheet, whereby the cover sheets adhere in a tacky manner onto the preheated substrate, by a hot-melt adhesive effect provided by the hot polypropylene. The bordering edges of the cover sheets forming the junction therebetween are then pressed down by a tucking blade from above so as to form the valley in the substrate and push the junction area of the cover sheets into the valley. Next, the valley is pinched together from below, while the tucking blade is retracted from above, so as to pinch the valley closed, whereby the junction of the two different cover sheets is held in the pinched valley.
By pinching the substrate in this manner, while pressing down from above with a tucking blade, and continuing and completing the pinching as the tucking blade is removed, it is ensured that the valley is pinched closed without leaving any gap or space resulting from the width or thickness of the tucking blade. The pinching securely adhesively fixes the bordering edges of the two different cover sheets onto the substrate in the valley, due to the tacky hot-melt adhesive effect of the hot substrate sheet, so that it is unnecessary to splice or bond the bordering edges to each other.
Since the pinching gap is initially much wider than the finished pinched valley, the degree of precision required for aligning or registering the junction line of the two different cover sheets over the pinching gap is significantly reduced. Namely, it is simply necessary to align the junction of the two cover sheets with the initially wide open gap in the molding tools used for forming the pinched valley, and when this gap is closed or pinched, the finished pinched valley is much narrower than the originally provide gap. Thus, the wider width of the initially open gap contributes to a larger tolerance for positioning the junction line of the two cover sheets, while the narrower closed gap defines the width of the finished valley pinching the cover sheet bordering edges therein.
Moreover, the depth of the pinching gap also contributes to the tolerance range for ultimately hiding the junction line of the two different cover sheet materials. By making the gap as deep and as wide as required in the initial open state of the molding tools, it is simple to provide a large tolerance for the proper positioning of the two different cover sheets onto the substrate and then positioning the substrate onto the mold, while still ensuring that the finished trim component will have a completely closed or pinched valley, with the junction of the two different cover sheets completely hidden within this valley. The resulting valley has a clean and crisp closed appearance, because the inner width of the substrate valley is not greater than the sum of the thicknesses of the two cover sheets overlapped and received in the pinched valley.
The above objects have still further been generally achieved in a forming mold apparatus according to the parent application and the present invention, including a lower mold section and an upper mold section that are generally movable vertically relative to each other. The molding apparatus further includes a slip frame that holds the edges of the substrate sheet with the cover an sheets placed thereon, and transports this prelaminated sheet into the mold and holds it under proper tension during the molding operation. The lower mold section includes a fixed base mold or fixed tool segment, a vertically movable primary lower mold stamp that is vertically movable relative to the fixed tool segment, and a pinching stamp that is horizontally movable relative to the fixed tool segment and that forms a pinching gap between a protruding edge or rim of the pinching stamp and a protruding edge or rim of the fixed tool segment. The upper mold section includes an upper primary mold stamp, a tucking blade that is vertically movable relative to the upper primary mold stamp, and an edge crimping ring that is vertically movable relative to the upper primary mold stamp.
The lower primary mold stamp cooperates with the upper primary mold stamp to form the major contours of the finished trim component therebetween. The tucking blade of the upper mold section cooperates with the pinching gap formed between the fixed tool segment and the horizontally movable pinching stamp of the lower mold section in order to form the pinched valley in the trim component, with the junction between the two different cover sheets tucked down into this closed pinched valley. The vertically movable edge crimping ring cooperates with a corresponding edge of the pinching stamp of the lower mold section to form a closed crimped edge around the outer contour of the trim component.
In practically carrying out the above described original method using the above described original apparatus according to the above referenced parent application, it has been discovered that the original method and apparatus could still be further improved. Namely, it is sometimes difficult to ensure that the junction between the two cover sheets remains precisely aligned in the valley of the substrate, even considering the range of tolerance that is afforded by this pinched valley as described above. Particularly, in practice it has been found that the two cover sheet materials adhered onto the substrate very often undergo differential slipping or differential stretching as the tucking blade of the upper mold section pushes the junction line of the two cover sheets into the pinching gap in the pinching stamp of the lower mold section.
Since the two cover sheets on the substrate are held under tension in the slip frame around the perimeter of the molding apparatus, the two cover sheets will purposely slip to some extent, depending on the tension applied respectively to the cover sheets. If the two respective cover sheets are made of two different materials respectively having different stretching or thermal yielding characteristics, or if the two cover sheets are of different sizes or are subjected to different degrees of molding on the opposite sides of the junction line, then these two cover sheets (and the underlying substrate) will apply different degrees of tension and will undergo differential slipping in the slip frame.
As a result, in practice, it has often been found that the junction line unintendedly slips laterally out of the pinching gap as the tucking blade pushes it down into the pinching gap. This phenomenon occurs particularly when the junction line or the molded contour along the junction line has a complex curvature or the like. In such a case, it has been found that the junction line will remain within the pinching gap (and thus within the finished pinched valley of the substrate) in some areas, while being shifted laterally out of the finished pinched valley of the substrate in other areas. The result is unsatisfactory, so that the affected pieces must be rejected.
To some extent, the above undesirable lateral slipping phenomenon can be avoided or compensated for by appropriately adjusting the clamping tension at different areas of the slip frame. However, any slight variations in the material characteristics of the two cover sheets, the process temperatures, the dimensions of the cover sheets, or the like, will again cause an unintended lateral slipping of the junction line relative to the valley in the substrate. It would be impractical and economically prohibitive to require mechanical readjustment or calibration of the slip frame tension on an ongoing or often-repeated basis.
In view of the above, the present invention provides an improved method and apparatus in comparison to the above referenced parent application, whereby this improved method and apparatus avoid the differential lateral slipping of the cover sheet materials relative to the intended junction line within the pinched valley of the substrate. This is achieved in general terms by positively holding the substrate and the two cover sheets directly along the junction line before and during the operation of pushing the cover sheet edges into the valley of the substrate and then pinching closed this valley. The present method and apparatus positively enforce the junction line of the two cover sheets to become a fixed reference line, relative to which all slipping or stretching will take place. By defining the fixed reference line along the junction line in this manner, the respectively required degree of slipping will take place at the various respective locations of the slip frame without allowing the junction line to shift laterally for compensating different tensions or the like. For this reason, it becomes possible to precisely position and pinch the junction line between two cover materials in a pinched valley of a substrate, even if this pinched valley of the substrate has a complex curved contour in two dimensions or three dimensions.
The improved method is carried out using an improved apparatus that includes the features of the original apparatus mentioned above, and additionally includes a counter-clamping blade in the lower mold section, which cooperates with the tucking blade of the upper mold section to clampingly hold the junction line of the two cover sheets therebetween. The counter-clamping blade is movably carried by piston rods or the like so that the counter-clamping blade can move up to meet the tucking blade with the substrate and cover sheets clampingly held therebetween, before any molding deformation of the substrate and cover sheets is carried out. Then the counter-clamping blade is retracted downwardly into the pinching gap of the lower mold section in unison as the tucking blade moves downwardly into the pinching gap. Thereafter, the pinching gap is closed while the tucking blade is retracted, generally in accordance with the original method.